Competition Clutch Part# 2-645-STU - Competition Clutch flywheels are made of 4140 forged steel and are a one-piece design. This helps significantly in reducing the chances of ring gear separation and friction surface warpage. All flywheels can be resurfaced. The correct flywheel step can be obtained in the CCI catalog or by calling us direct. Flywheel weights vary from 8lbs to 18lbs depending on application. The ultra lightweight steel flywheel (STU suffix) is recommended for forced induction and/or track and rally racing applications. This flywheel is machined with less material to assist in quicker revving capabilities. Well-suited for Stage 3 and up clutch applications. These flywheels will work with ALL performance and stock clutch assemblies. Not all applications have the ST and STU versions available. Please verify before ordering. All flywheels are SFI certified.